/*
    RNC decompression library. Copyright and ownership status unknown.

    Original code was from http://www.yoda.arachsys.com/dk/utils.html, but that
    site nor the code itself states any ownership or copyright claims.
    Modifications made to the original code include:
      * Const correctness
      * Prebuilt CRC table
      * Indentation and code style
*/

#include "th.h"

#define RNC_OK                  0
#define RNC_FILE_IS_NOT_RNC    -1
#define RNC_HUF_DECODE_ERROR   -2
#define RNC_FILE_SIZE_MISMATCH -3
#define RNC_PACKED_CRC_ERROR   -4
#define RNC_UNPACKED_CRC_ERROR -5
#define RNC_SIGNATURE 0x524E4301       /* "RNC\001" */

static const unsigned short rnc_crc_table[256] = {
    0x0000, 0xC0C1, 0xC181, 0x0140, 0xC301, 0x03C0, 0x0280, 0xC241,
    0xC601, 0x06C0, 0x0780, 0xC741, 0x0500, 0xC5C1, 0xC481, 0x0440,
    0xCC01, 0x0CC0, 0x0D80, 0xCD41, 0x0F00, 0xCFC1, 0xCE81, 0x0E40,
    0x0A00, 0xCAC1, 0xCB81, 0x0B40, 0xC901, 0x09C0, 0x0880, 0xC841,
    0xD801, 0x18C0, 0x1980, 0xD941, 0x1B00, 0xDBC1, 0xDA81, 0x1A40,
    0x1E00, 0xDEC1, 0xDF81, 0x1F40, 0xDD01, 0x1DC0, 0x1C80, 0xDC41,
    0x1400, 0xD4C1, 0xD581, 0x1540, 0xD701, 0x17C0, 0x1680, 0xD641,
    0xD201, 0x12C0, 0x1380, 0xD341, 0x1100, 0xD1C1, 0xD081, 0x1040,
    0xF001, 0x30C0, 0x3180, 0xF141, 0x3300, 0xF3C1, 0xF281, 0x3240,
    0x3600, 0xF6C1, 0xF781, 0x3740, 0xF501, 0x35C0, 0x3480, 0xF441,
    0x3C00, 0xFCC1, 0xFD81, 0x3D40, 0xFF01, 0x3FC0, 0x3E80, 0xFE41,
    0xFA01, 0x3AC0, 0x3B80, 0xFB41, 0x3900, 0xF9C1, 0xF881, 0x3840,
    0x2800, 0xE8C1, 0xE981, 0x2940, 0xEB01, 0x2BC0, 0x2A80, 0xEA41,
    0xEE01, 0x2EC0, 0x2F80, 0xEF41, 0x2D00, 0xEDC1, 0xEC81, 0x2C40,
    0xE401, 0x24C0, 0x2580, 0xE541, 0x2700, 0xE7C1, 0xE681, 0x2640,
    0x2200, 0xE2C1, 0xE381, 0x2340, 0xE101, 0x21C0, 0x2080, 0xE041,
    0xA001, 0x60C0, 0x6180, 0xA141, 0x6300, 0xA3C1, 0xA281, 0x6240,
    0x6600, 0xA6C1, 0xA781, 0x6740, 0xA501, 0x65C0, 0x6480, 0xA441,
    0x6C00, 0xACC1, 0xAD81, 0x6D40, 0xAF01, 0x6FC0, 0x6E80, 0xAE41,
    0xAA01, 0x6AC0, 0x6B80, 0xAB41, 0x6900, 0xA9C1, 0xA881, 0x6840,
    0x7800, 0xB8C1, 0xB981, 0x7940, 0xBB01, 0x7BC0, 0x7A80, 0xBA41,
    0xBE01, 0x7EC0, 0x7F80, 0xBF41, 0x7D00, 0xBDC1, 0xBC81, 0x7C40,
    0xB401, 0x74C0, 0x7580, 0xB541, 0x7700, 0xB7C1, 0xB681, 0x7640,
    0x7200, 0xB2C1, 0xB381, 0x7340, 0xB101, 0x71C0, 0x7080, 0xB041,
    0x5000, 0x90C1, 0x9181, 0x5140, 0x9301, 0x53C0, 0x5280, 0x9241,
    0x9601, 0x56C0, 0x5780, 0x9741, 0x5500, 0x95C1, 0x9481, 0x5440,
    0x9C01, 0x5CC0, 0x5D80, 0x9D41, 0x5F00, 0x9FC1, 0x9E81, 0x5E40,
    0x5A00, 0x9AC1, 0x9B81, 0x5B40, 0x9901, 0x59C0, 0x5880, 0x9841,
    0x8801, 0x48C0, 0x4980, 0x8941, 0x4B00, 0x8BC1, 0x8A81, 0x4A40,
    0x4E00, 0x8EC1, 0x8F81, 0x4F40, 0x8D01, 0x4DC0, 0x4C80, 0x8C41,
    0x4400, 0x84C1, 0x8581, 0x4540, 0x8701, 0x47C0, 0x4680, 0x8641,
    0x8201, 0x42C0, 0x4380, 0x8341, 0x4100, 0x81C1, 0x8081, 0x4040,
};

struct bit_stream
{
    unsigned long bitbuf;           /* holds between 16 and 32 bits */
    int bitcount;               /* how many bits does bitbuf hold? */
};

struct huf_table
{
    int num;                   /* number of nodes in the tree */
    struct
    {
        unsigned long code;
        int codelen;
        int value;
    } table[32];
};

/*
 * Calculate a CRC, the RNC way.
 */
static long rnc_crc(const unsigned char* data, long len)
{
    unsigned short val = 0;

    while(len--)
    {
        val ^= *data++;
        val = (val >> 8) ^ rnc_crc_table[val & 0xFF];
    }

    return val;
}


/*
 * Return the big-endian longword at p.
 */
static unsigned long blong (const unsigned char *p)
{
    unsigned long n;
    n = p[0];
    n = (n << 8) + p[1];
    n = (n << 8) + p[2];
    n = (n << 8) + p[3];
    return n;
}

/*
 * Return the little-endian longword at p.
 */
static unsigned long llong (const unsigned char *p)
{
    unsigned long n;
    n = p[3];
    n = (n << 8) + p[2];
    n = (n << 8) + p[1];
    n = (n << 8) + p[0];
    return n;
}

/*
 * Return the big-endian word at p.
 */
static unsigned long bword (const unsigned char *p)
{
    unsigned long n;
    n = p[0];
    n = (n << 8) + p[1];
    return n;
}

/*
 * Return the little-endian word at p.
 */
static unsigned long lword (const unsigned char *p)
{
    unsigned long n;
    n = p[1];
    n = (n << 8) + p[0];
    return n;
}

/*
 * Mirror the bottom n bits of x.
 */
static unsigned long mirror (unsigned long x, int n)
{
    unsigned long top = 1 << (n-1), bottom = 1;
    while (top > bottom)
    {
        unsigned long mask = top | bottom;
        unsigned long masked = x & mask;
        if (masked != 0 && masked != mask)
        {
            x ^= mask;
        }
        top >>= 1;
        bottom <<= 1;
    }
    return x;
}


/*
 * Initialises a bit stream with the first two bytes of the packed
 * data.
 */
static void bitread_init (bit_stream *bs, const unsigned char **p)
{
    bs->bitbuf = lword (*p);
    bs->bitcount = 16;
}

/*
 * Fixes up a bit stream after literals have been read out of the
 * data stream.
 */
static void bitread_fix (bit_stream *bs, const unsigned char **p)
{
    bs->bitcount -= 16;
    bs->bitbuf &= (1<<bs->bitcount)-1; /* remove the top 16 bits */
    bs->bitbuf |= (lword(*p)<<bs->bitcount);/* replace with what's at *p */
    bs->bitcount += 16;
}

/*
 * Returns some bits.
 */
static unsigned long bit_peek (bit_stream *bs, const unsigned long mask)
{
    return bs->bitbuf & mask;
}

/*
 * Advances the bit stream.
 */
static void bit_advance (bit_stream *bs, int n, const unsigned char **p)
{
    bs->bitbuf >>= n;
    bs->bitcount -= n;
    if (bs->bitcount < 16)
    {
        (*p) += 2;
        bs->bitbuf |= (lword(*p)<<bs->bitcount);
        bs->bitcount += 16;
    }
}

/*
 * Reads some bits in one go (ie the above two routines combined).
 */
static unsigned long bit_read (bit_stream *bs, unsigned long mask, int n, const unsigned char **p)
{
    unsigned long result = bit_peek(bs, mask);
    bit_advance(bs, n, p);
    return result;
}

/*
 * Read a Huffman table out of the bit stream and data stream given.
 */
static void read_huftable(huf_table *h, bit_stream *bs, const unsigned char **p)
{
    int i, j, k, num;
    int leaflen[32];
    int leafmax;
    unsigned long codeb;           /* big-endian form of code */

    num = bit_read(bs, 0x1F, 5, p);

    if(num == 0)
    {
        return;
    }

    leafmax = 1;
    for(i = 0; i < num; i++)
    {
        leaflen[i] = bit_read(bs, 0x0F, 4, p);
        if (leafmax < leaflen[i])
        {
            leafmax = leaflen[i];
        }
    }

    codeb = 0L;
    k = 0;
    for(i = 1; i <= leafmax; i++)
    {
        for(j = 0; j < num; j++)
        {
            if(leaflen[j] == i)
            {
                h->table[k].code = mirror(codeb, i);
                h->table[k].codelen = i;
                h->table[k].value = j;
                codeb++;
                k++;
            }
        }
        codeb <<= 1;
    }
    h->num = k;
}

/*
 * Read a value out of the bit stream using the given Huffman table.
 */
static unsigned long huf_read(huf_table *h, bit_stream *bs, const unsigned char **p)
{
    int i;
    unsigned long val;

    for (i = 0; i < h->num; i++)
    {
        unsigned long mask = (1 << h->table[i].codelen) - 1;
        if(bit_peek(bs, mask) == h->table[i].code)
        {
            break;
        }
    }
    if(i == h->num)
    {
        return -1;
    }
    bit_advance(bs, h->table[i].codelen, p);

    val = h->table[i].value;

    if (val >= 2)
    {
        val = 1 << (val-1);
        val |= bit_read(bs, val-1, h->table[i].value - 1, p);
    }
    return val;
}

static int rnc_unpack(const unsigned char* input, unsigned char* output)
{
    const unsigned char *inputend;
    unsigned char *outputend;
    bit_stream bs;
    huf_table raw, dist, len;
    unsigned long ch_count;
    unsigned long ret_len;
    unsigned out_crc;
    if(blong(input) != RNC_SIGNATURE)
    {
        return RNC_FILE_IS_NOT_RNC;
    }
    ret_len = blong(input + 4);
    outputend = output + ret_len;
    inputend = input + 18 + blong(input + 8);

    input += 18;               /* skip header */

    /*
     * Check the packed-data CRC. Also save the unpacked-data CRC
     * for later.
     */
    if(rnc_crc(input, inputend-input) != bword(input - 4))
    {
        return RNC_PACKED_CRC_ERROR;
    }
    out_crc = bword(input - 6);

    bitread_init(&bs, &input);
    bit_advance(&bs, 2, &input);      /* discard first two bits */

    /*
     * Process chunks.
     */
    while (output < outputend)
    {
        read_huftable(&raw, &bs, &input);
        read_huftable(&dist, &bs, &input);
        read_huftable(&len, &bs, &input);
        ch_count = bit_read(&bs, 0xFFFF, 16, &input);

        while(true)
        {
            long length, posn;

            length = huf_read(&raw, &bs, &input);
            if(length == -1)
            {
                return RNC_HUF_DECODE_ERROR;
            }
            if(length)
            {
                while(length--)
                    *output++ = *input++;
                bitread_fix(&bs, &input);
            }
            if(--ch_count <= 0)
            {
                break;
            }

            posn = huf_read(&dist, &bs, &input);
            if(posn == -1)
            {
                return RNC_HUF_DECODE_ERROR;
            }
            length = huf_read(&len, &bs, &input);
            if(length == -1)
            {
                return RNC_HUF_DECODE_ERROR;
            }
            posn += 1;
            length += 2;
            while(length--)
            {
                *output = output[-posn];
                output++;
            }
        }
    }

    if(outputend != output)
    {
        return RNC_FILE_SIZE_MISMATCH;
    }

    /*
     * Check the unpacked-data CRC.
     */
    if(rnc_crc(outputend - ret_len, ret_len) != out_crc)
    {
        return RNC_UNPACKED_CRC_ERROR;
    }

    return RNC_OK;
}

unsigned char* THAnimations::Decompress(unsigned char* pData, size_t& iLength)
{
    unsigned long outlen = blong(pData + 4);
    unsigned char* outbuf = new unsigned char[outlen];
    if(rnc_unpack(pData, outbuf) == RNC_OK)
    {
        delete[] pData;
        iLength = outlen;
        return outbuf;
    }
    else
    {
        delete[] pData;
        delete[] outbuf;
        iLength = 0;
        return NULL;
    }
}
